Positive type radiation-sensitive composition and process for producing pattern with the same

ABSTRACT

The present invention relates to a positive-working radiation-sensitive composition which is characterized in that it contains a compound meeting any of conditions a1) to a3), and b) an acid generator which generates acid by irradiation with radiation; and also to a method for the production of a resist pattern employing same. 
     a1) A compound wherein a carboxyl group is protected by an acid labile group represented by general formula (1) 
                 
 
(R 1  and R 2  are aromatic rings, and R 3  represents an alkyl group, a substituted alkyl group, a cycloalkyl group or an aromatic ring. R 1  to R 3  may be the same or different.)
 
     a2) A compound in which an alkali-soluble group is protected by an acid labile group represented by general formula (2) 
                 
 
(R 4  to R 6  are each an alkyl group, a substituted alkyl group, a cycloalkyl group or an aromatic ring, and at least one of R 4  to R 6  is an aromatic ring with an electron-donating group. R 4  to R 6  may be the same or different.)
 
     a3) A compound in which an alkali-soluble group is protected by an acid labile group a, and either acid labile group a has an alkali-soluble group or acid labile group a has an alkali-soluble group protected by an acid labile group b. 
     With this constitution, it is possible by means of the present invention to obtain a positive-working radiation-sensitive composition of high sensitivity having a resolution which enables sub-quarter micron pattern processing to be carried out.

TECHNICAL FIELD

The present invention relates to a positive-working radiation-sensitivecomposition used in the production of semiconductor integrated circuits,lithography masks and the like.

TECHNICAL BACKGROUND

Along with the increasing degree of integration in recent years,patterns are becoming ever finer in fields such as the production ofsemiconductor circuits and lithography masks. As a result, resistmaterials of still higher resolution levels are required, and it hasbecome necessary to be able to carry out the processing of <0.25 μmsub-quarter micron patterns at high sensitivity. Carrying out suchminute processing by conventional lithography using a comparatively longwavelength light source is difficult, and lithography employing higherenergy X-rays, electron beams and vacuum ultraviolet is beinginvestigated, and resists corresponding to these radiation sources arebeing demanded.

As known resist materials having the characteristics of high sensitivityand high resolution corresponding to such sources of radiation exposure,chemically amplified resists have been extensively investigated.Chemically amplified resists are resists which possess a mechanismwhereby acid is generated in exposed regions due to the action of aphotoacid generator, and the solubility of the exposed regions ismodified by the catalytic action of this acid. Hitherto, amongst suchchemically-amplified resists those showing comparatively good resistproperties have employed alkali-soluble resins in which thealkali-soluble groups are protected by acid labile groups such as thetert-butyl group, the 1,1-diphenylethyl group (U.S. Pat. No. 5,688,628),the trityl group (JP-A-6-83057) and other such tertiary ester groups,the tert-butoxycarbonyl group, the acetal group and the like.

However, there is an opposing relation between resolution andsensitivity, and there have been problems such as inadequate sensitivitywhen obtaining a resolution sufficient for carrying out sub-quartermicron pattern processing.

DISCLOSURE OF THE INVENTION

The present invention relates to a positive-working radiation-sensitive,composition which is characterized in that it contains any of compoundsal) to a3), plus b) an acid generator which generates acid by exposureto radiation; and to a method of producing a resist pattern employingsame.

a1) A compound in which a carboxyl group is protected by an acid labilegroup represented by general formula (1)

(R¹ and R² are aromatic rings, and R³ represents an alkyl group, asubstituted alkyl group, a cycloalkyl group or an aromatic ring; and R¹to R³ may be the same or different.)

a2) A compound in which an alkali-soluble group is protected by an acidlabile group represented by general formula (2).

(R⁴ to R⁶ are each an alkyl group, a substituted alkyl group, acycloalkyl group or an aromatic ring, and at least one of R⁴ to R⁶ is anaromatic ring with an electron-donating group. R⁴ to R⁶ may be the sameor different.)

a3) A compound in which an alkali-soluble group is protected by an acidlabile group a, and the acid labile group a has an alkali-soluble groupor alternatively the acid labile group a has an alkali-soluble groupprotected by an acid labile group b.

OPTIMUM FORM FOR PRACTISING THE INVENTION

The positive-working radiation-sensitive composition of the presentinvention comprises any of compounds a1) to a3), plus b) an acidgenerator which generates acid by exposure to radiation.

Compound a1) is a compound wherein a carboxyl group is protected by anacid labile group represented by general formula (1). R¹ and R² arearomatic rings, and R³ represents an alkyl group, a substituted alkylgroup, a cycloalkyl group or an aromatic ring. R¹ to R³ may be the sameor different. Specific examples of R¹ and R² are the phenyl group,naphthyl group, pyridyl group, furyl group and thienyl group. Specificexamples of R³ are the methyl group, ethyl group, propyl group, butylgroup, methoxymethyl group, ethoxybutyl group, hydroxy-ethyl group andcyclohexyl group, and also the groups cited above as specific examplesof R¹. By introducing two or more aromatic rings onto the tertiarycarbon bonded to the oxygen, it is possible by the aromatic ringresonance effect to facilitate the elimination reaction of the labilegroup by the acid, and the resist sensitivity is markedly enhancedcompared to the case where there are no aromatic rings on the tertiarycarbon or just one. Furthermore, by introducing several aromatic rings,the dry etching resistance is enhanced.

Compound a2) is a compound in which an alkali-soluble group is protectedby an acid labile group represented by general formula (2). R⁴ to R⁶ areeach an alkyl group, a substituted alkyl group, a cycloalkyl group or anaromatic ring, and at least one of R⁴ to R⁶ is an aromatic ring with anelectron-donating group. R⁴ to R⁶ may be the same or different. Here,the electron-donating group is a group having a stronger tendency todonate electrons than hydrogen, and examples include acyloxy groups,amino groups, alkyl groups and alkoxy groups. The electron-donatinggroups which are preferably used from amongst these are acyloxy groupwith 2 to 6 carbons, alkyl groups with 1 to 4 carbons and alkoxy groupswith 1 to 6 carbons, of which the alkoxy groups with 1 to 6 carbons aremost preferred. There may also be two or more electron-donating groupson one aromatic ring. Specific examples of aromatic rings with anelectron-donating group are the 4-acetyloxyphenyl group,4-acetyloxynaphthyl group, 3-benzyloxyphenyl group,4-dimethylaminophenyl group, 2-dimethylaminophenyl group,4-aminonaphthyl group, p-tolyl group, m-tolyl group, o-tolyl group,2,4-dimethylphenyl group, 2,4,6-trimethylphenyl group,4-tert-butylphenyl group, 4-methylnaphthyl group, 4-methoxyphenyl group,2-methoxyphenyl group, 3-ethoxyphenyl group, 4-tert-butoxyphenyl group,4-phenoxyphenyl group, 4-methoxynaphthyl group, 3-isopropoxyphenylgroup, 4-methoxy-3-methylphenyl group, 3,5-dimethoxyphenyl group and thelike. Furthermore, as specific examples of the remaining groups amongstR⁴ to R⁶ other than the aromatic ring with an electron-donating group,there are the methyl group, ethyl group, propyl group, butyl group,methoxymethyl group, ethoxybutyl group, hydroxyethyl group, cyclohexylgroup and phenyl group. When an aromatic ring on a tertiary carbonbonded to oxygen possesses an electron-donating group, the positivecharge of the carbocation produced at the time of deprotection isstabilized, so deprotection is facilitated and the resist sensitivity isenhanced. Furthermore, the carboxyl group and the phenolic hydroxylgroup are preferred as the alkali-soluble group in compound a2).

A structure represented by the following general formula (3) ispreferred as the aromatic ring with an electron-donating group containedin the acid labile group of general formula (2).

R⁸, R¹⁰ and R¹² each independently represents a hydrogen atom, an alkylgroup with 1 to 4 carbons or an alkoxy group with 1 to 6 carbons, withat least one of these being such an alkyl group or alkoxy group. R⁹ andR¹¹ each independently represents a hydrogen atom, an alkyl group with 1to 4 carbons or an alkoxy group with 1 to 6 carbons. Still greatersensitivity is realized by introducing an electron-donating group at theortho- or para-position.

Compound a3) is a compound in which an alkali-soluble group is protectedby an acid labile group a, and this acid labile group a has analkali-soluble group or alternatively acid labile group a has analkali-soluble group protected by an acid labile group b. Acid labilegroup a and acid labile group b may have the same structure. Acid labilegroup a preferably either has at least one phenolic hydroxyl group orcarboxyl group, or this phenolic hydroxyl group or carboxyl group isfurther protected by acid labile group b. The groups represented bygeneral formula (4) may be given as examples of the structure of such anacid labile group a.

R¹³ to R¹⁵ are each independently an alkyl group, a substituted alkylgroup, a cycloalkyl group, an aryl group, a substituted aryl group, agroup containing an alkali-soluble group, or a group containing analkali-soluble group protected by acid labile group b, with at least onebeing a group containing an alkali-soluble group, or a group containingan alkali-soluble group protected by acid labile group b. R¹³ to R¹⁵ maybe the same or different. Here, at least one of R¹³ to R¹⁵ in generalformula (4) is preferably a group represented by general formulae (5) or(6).

A represents an alkylene group with 1 to 4 carbons, an arylene groupwith 6 to 10 carbons or a single bond. B represents an alkylene groupwith 1 to 6 carbons, an arylene group with 6 to 10 carbons, analkylenearylene group with 7 to 12 carbons or a single bond. R¹⁶ to R¹⁹each independently represents a hydrogen atom or an alkyl group with 1to 4 carbons. Y represents acid labile group b or a hydrogen atom, and mis 1 to 3. It is particularly preferred in terms of the sensitivity thatat least one of R¹³ to R¹⁵ in general formula (4) be a group representedby general formulae (7) or (8).

Here, R²⁰ and R²¹ each independently represents a hydrogen atom or analkyl group with 1 to 4 carbons. Y represents an acid labile group b ora hydrogen atom, and in is 1 to 3. Furthermore, R²² and R²³ represent ahydrogen atom or an alkyl group with 1 to 4 carbons. Y represents anacid labile group b or a hydrogen atom. Examples of acid labile group bare the methoxymethyl group, inethyithiomethyl group, ethoxymethylgroup, ethyithiomethyl group, methoxyethoxymethyl group, benzyloxymethylgroup, benzylthiomethyl group, phenacyl group, bromophenacyl group,methoxyphenacyl group, methylthiophenacyl group, α-methylphenacyl group,cyclopropylmethyl group, benzyl group, diphenylmethyl group,triphenylmethyl group, bromobenzyl group, nitrobenzyl group,methoxybenzyl group, methylthiobenzyl group, ethoxybenzyl group,methoxycarbonylmethyl group, ethoxycarbonylmethyl group,n-propoxycarbonylmethyl group, isopropoxycarbonylmethyl group,n-butoxycarbonylmethyl group, tert-butoxycarbonylmethyl group, propenylgroup, 1-methoxyethyl group, 1-methylthioethyl group, 1,1-dimethoxyethyl group, 1-ethoxyethyl group, 1-ethylthioethyl group,1,1-dimethoxyethyl group, 1-phenoxyethyl group, 1-phenylthioethyl group,1,1-diphenoxyethyl group, 1-benzyloxyethyl group, 1-benzylthioethylgroup, 1-cyclopropylethyl group, 1-phenylethyl group, 1,1-diphenylethylgroup, 1-methoxycarbonylethyl group, 1-ethoxycarbonylethyl group,1-n-propoxycarbonylethyl group, 1-isopropoxycarbonylethyl group,1-n-butoxycarbonylethyl group, 1-tert-butoxycarbonylethyl group,isopropyl group, sec-butyl group, tert-butyl group, 1,1-dimethylbutylgroup, trimethylsilyl group, ethyldimethylsilyl group,methyldiethylsilyl group, triethylsilyl group, isopropyldimethylsilylgroup, methyldiisopropylsilyl group, triisopropylsilyl group,tert-butyldimethylsilyl group, methyldi-tert-butylsilyl group,tri-tert-butylsilyl group, phenyldimethylsilyl group,methyldiphenylsilyl group, triphenylsilyl group, methoxycarbonyl group,ethoxycarbonyl group, isopropoxycarbonyl group, tert-butoxycarbonylgroup, acetyl group, propionyl group, butyryl group, heptanoyl group,hexanoyl group, valeryl group, pivaloyl group, isovaleryl group, lauroylgroup, myristoyl group, palmitoyl group, stearoyl group, oxalyl group,malonyl group, succinyl group, glutaryl group, adipoyl group, pimeloylgroup, suberoyl group, azelaoyl group, sebacoyl group, acryloyl group,propionyl group, methacryloyl group, crotonoyl group, oleoyl group,maleoyl group, fumaroyl group, mesaconoyl group, benzoyl group,phthaloyl group, isophthaloyl group, terephthaloyl group, naphthoylgroup, toluoyl group, hydroatropoyl group, atropoyl group, cinnamoylgroup, furoyl acid, thenoyl group, nicotinoyl group, isonicotinoylgroup, p-toluenesulphonyl group, mesyl group, cyclopropyl group,cyclopentyl group, cyclohexyl group, cyclohexenyl group,4-methoxycyclohexyl group, tetrahydropyranyl group, tetrahydrofuranylgroup, tetrahydrothiopyranyl group, tetrahydrothiofuranyl group,3-bromotetrahydropyranyl group, 4-methoxytetrahydropyranyl group,4-methoxytetrahydrothiopyranyl group and the like.

The compounds of conditions a1) to a3) are preferably polymers. Theweight average molecular weight measured by GPC (gel permeationchromatography) based on polystyrene conversion will be 4,000-1,000,000,preferably 5,000-100,000, and more preferably 5,000-50,000. With aweight average molecular weight of less than 5,000, film formationbecomes difficult, while with a weight average molecular weight of morethan 50,000 the resist sensitivity is lowered.

Still further preferred as the compounds of al) to a3) are polymerscontaining structural units represented by the following general formula(9). R²⁴ represents a hydrogen atom, an alkyl group with 1 to 4 carbons,a cyano group or a halogen. Z is a group represented by general formula(1), (2) or (4).

Furthermore, as the compounds of a2) or a3), polymers containingstructural units represented by the following general formula (10) arepreferred. R²⁵ represents a hydrogen atom, an alkyl group with 1 to 4carbons, a cyano group or a halogen. X is an acid labile grouprepresented by general formula (2) or (4).

In order to obtain such polymer, there may be synthesized for examplemonomer with a structure in which the carboxyl group of acrylic acid ormethacrylic acid is protected by an acid labile group represented bygeneral formula (1), or monomer of structure in which the hydroxyl groupof p-hydroxystyrene is protected by an acid labile group represented bygeneral formula (2), and then polymerization carried out usingazobisisobutyronitrile or the like.

Furthermore, in the structural units represented by general formula (9),it is more preferred that R²⁴ be a cyano group or halogen. When polymerwith such a structure is exposed to radiation, the polymer chains arereadily cleaved and the molecular weight lowered. As a result, thesolubility of the exposed regions is raised and there is produced highsensitivity and high contrast.

Specific examples of the structural units represented by aforesaidgeneral formulae (9) and (10) are as follows.

The polymer containing the structural units represented by generalformula (9) or (10) may be a polymer containing only structural unitsrepresented by general formula (9) or (10), but it may also be a polymercontaining other monomer units providing the characteristics as achemically amplified resist are not impaired. Examples of other monomerstructures are acrylic acid, methyl acrylate, ethyl acrylate,hydroxyethyl methacrylate, isopropyl acrylate, n-butyl acrylate,tert-butyl acrylate, methacrylic acid, methyl methacrylate, ethylmethacrylate, hydroxyethyl acrylate, isopropyl methacrylate, n-butylmethacrylate, tert-butyl methacrylate, methyl α-chloroacrylate, ethylα-chloroacrylate, hydroxyethyl α-chloroacrylate, isopropylα-chloroacrylate, n-butyl α-chloroacrylate, tert-butyl α-chloroacrylate,methyl α-cyanoacrylate, ethyl α-cyanoacrylate, hydroxyethylα-cyanoacrylate, isopropyl α-cyanoacrylate, n-butyl α-cyanoacrylate,styrene, p-hydroxystyrene, α-methylstyrene, α-methyl-p-hydroxystyrene,maleic acid, maleic anhydride, crotonic acid, fumaric acid, mesaconicacid, citraconic acid, itaconic acid, itaconic anhydride, acrylonitrile,methacrylonitrile, crotonic nitrile, maleonitrile, fumaronitrile,metaconic nitrile, citraconic nitrile, itaconic nitrile, acrylamide,methacrylamide, crotonic amide, maleamide, fumaramide, mesaconic amide,citraconic amide, itaconic amide, vinylaniline, vinyl-pyrrolidone,vinylimidazole and the like. In the case where the other monomer unitshave an alkali-soluble group, this alkali-soluble group can be protectedwith an acid labile group. Specific examples of the acid labile groupare those given as examples of acid labile group b.

Furthermore, the polymer containing structural units represented byaforesaid general formula (9) or (10) preferably used in the presentinvention may also contain the following cyclic structures in the mainchain in order to enhance the dry etching resistance, etc.

The positive-working radiation-sensitive composition of the presentinvention also contains b), an acid generator which generates acid byexposure to radiation. In this way, by making possible pattern formationbased on the chemical amplification mechanism, it is possible to obtaina high resolution pattern at high sensitivity. The acid generatoremployed here may be of any kind providing that, as a result of the acidgenerated, the rate of dissolution of the compound of al) to a3) inaqueous alkali solution is increased, and as examples thereof there areonium salts, halogen-containing compounds, diazoketone compounds,diazomethane compounds, sulphone compounds, sulphonic acid estercompounds, sulphonimide compounds and the like.

As specific examples of the onium salts, there are diazonium salts,ammonium salts, iodonium salts, sulphonium salts, phosphonium salts,oxonium salt and the like. Preferred examples of the onium salts arediphenyliodonium triflate, diphenyliodonium pinenesuphonate,diphenyliodonium dodecylbenzene-sulphonate, triphenylsulphoniumtriflate, triphenylsulphonium hexafluoroantimonate, triphenylsulphoniumnaphthalenesulphonate, (hydroxyphenyl)benzylmethylsulphoniumtoluenesulphonate and the like.

As specific examples of the halogen-containing compounds there arehydrocarbon compounds containing haloalkyl groups and heterocycliccompounds containing haloalkyl groups. Preferred halogen-containingcompounds are 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-napthyl-4,6-bis(trichloromethyl)-s-triazine and the like.

Specific examples of the diazoketone compounds are 1,3-diketo-2-diazocompounds, diazobenzoquinone compounds, diazonaphthoquinone compoundsand the like. As examples of preferred diazoketone compounds, there arethe ester of 2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-4-Sulphonic acid, and the ester of1,1,1-tris(4-hydroxyphenyl)ethane and1,2-naphthoquinonediazide-4-sulphonic acid.

Specific examples of the diazomethane compounds arebis(trifluoromethylsulphonyl)diazomethane,bis(cyclohexylsulphonyl)diazomethane, bis(phenylsulphonyl)diazomethane,bis(p-tolylsulphonyl)diazomethane, bis(2,4-xylylsulphonyl)diazomethane,bis(p-chlorophenylsulphonyl)diazomethane,methylsulphonyl-p-toluenesulphonyldiazomethane,cyclohexylsulphonyl(1,1-dimethylethylsulphonyl)diazomethane,bis(1,1-dimethylethylsulphonyl)diazomethane,phenylsulphonyl(benzoyl)diazomethane and the like.

Specific examples of the sulphone compounds are β-ketosulphone compoundsand β-sulphonylsulphone compounds. Preferred examples of such compoundsare 4-trisphenacylsulphone, mesitylphenacylsulphone andbis(phenylsulphonyl)methane.

Examples of the sulphonic acid ester compounds are alkylsulphonates,haloalkylsulphonates, arylsulphonates, imino-sulphonates and the like.Specific examples of the sulphonic acid compounds are benzoin tosylate,pyrogallol trimesylate, nitrobenzyl-9,10-diethoxyanthracene-2-sulphonateand the like.

Specific examples of the sulphonimide compounds areN-(trifluoromethylsulphonyloxy)succinimide,N-(trifluoromethylsulphonyloxy)phthalimide,N-(trifluoromethylsulphonyloxy)diphenylmaleimide,N-(trifluoromethylsulphonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(trifluoromethylsulphonyloxy)-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(camphorsulphonyloxy)bicyclo[2.2.1]heptane-5,6-oxy-2,3-dicarboxylimide,N-(trifluoromethylsulphonyloxy)naphthyldicarboxylimide,N-(camphorsulphonyloxy)succinimide, N-(camphorsulphonyloxy)phthalimide,N-(camphorsulphonyloxy)diphenylmaleimide,N-(camphorsulphonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(camphorsulphonyloxy)-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(camphorsulphonyloxy)bicyclo[2.2.1]heptane-5,6-oxy-2,3-dicarboxylimide,N-(camphorsulphonyloxy)naphthyldicarboxylimide,N-(4-methylphenylsulphonyloxy)succinimide,N-(4-methylphenylsulphonyloxy)phthalimide,N-(4-methylphenylsulphonyloxy)diphenylmaleimide,N-(4-methylphenylsulphonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(4-methylphenylsulphonyloxy)-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(4-methylphenylsulphonyloxy)bicyclo[2.2.1]heptan-5,6-oxy-2,3-dicarboxylimide,N-(4-methylphenylsulphonyloxy)naphthyldicarboxylimide,N-(2-trifluoromethylphenylsulphonyloxy)succinimide,N-(2-trifluoromethylphenylsulphonyloxy)phthalimide,N-(2-trifluoromethylphenylsulphonyloxy)diphenylmaleimide,N-(2-trifluoromethylphenylsulphonyloxy)bicycl[2.2. 1]hept-5-ene-2,3-dicarboxylimide, N-(2-trifluoromethylphenylsulphonyloxy)-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(2-trifluoromethylphenylsulphonyloxy)bicyclo[2.2.1]heptane-5,6-oxy-2,3-dicarboxylimide,N-(2-trifluoromethylphenylsulphonyloxy)naphthyldicarboxyl-imide,N-(4-fluorophenylsulphonyloxy)succinimide,N-(2-fluorophenylsulphonyloxy)phthalimide,N-(4-fluorophenylsulphonyloxy)diphenylmaleimide,N-(4-fluorophenylsulphonyloxy)bicyclo[2.2.l]hept-5-ene-2,3-dicarboxylimide,N-(4-fluorophenylsulphonyloxy)-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylimide,N-(4-fluorophenylsulphonyloxy)bicyclo[2.2.1]heptane-5,6-oxy-2,3-dicarboxylimide,N-(4-fluorophenylsulphonyloxy)naphthyldicarboxylimide and the like.

These acid generators can be used on their own or they can be used inthe form of mixtures of two or more. The amount of the acid generatoradded is normally from 0.01 to 50 wt % in terms of the polymer, and morepreferably 0.1 to 10 wt %. With less than 0.01 wt %, pattern formationbecomes impossible, while with more than 50 wt % the affinity for thedeveloper liquid is lowered and developing faults and the like arise.

The positive-working radiation-sensitive composition of the presentinvention may include alkali-soluble resin.

Where required, there may also be included in the positive-workingradiation-sensitive composition of the present invention additives suchas surfactants, sensitizers, stabilizers, antifoaming agents, aciddiffusion inhibitors and the like.

The positive-working radiation-sensitive composition of the presentinvention is obtained by dissolving the aforesaid components in asolvent. The amount of solvent used is not particularly restricted butis adjusted such that the solids content is from 5 to 35 wt %. Examplesof preferably-used solvents are solvents selected from esters such asethyl acetate, butyl acetate, amyl acetate, ethyl propionate, methylacetate, methyl benzoate, methyl lactate, ethyl lactate, ethyl pyruvate,methyl β-isobutyrate, methyl 3-methoxypropionate, ethyl3-ethoxypropionate and γ-butyrolactone, Cellosolves such as MethylCellosolve, Ethyl Cellosolve and Butyl Cellosolve, Cellosolve esterssuch as Methyl Cellosolve Acetate, Ethyl Cellosolve Acetate and ButylCellosolve Acetate, propylene glycol esters such as propylene glycolmonomethyl ether acetate and propylene glycol monoethyl ether acetate,ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuranand anisole, ketones such as methyl ethyl ketone, methyl isobutylketone, methyl-n-amyl ketone, cyclohexanone and isophorone, and aproticsolvents such as dimethylformamide, dimethylacetamide,N-methylpyrrolidone, dimethylsulphoxide, sulfolane and the like, andcombinations of such solvents.

The positive-working radiation-sensitive composition of the presentinvention is employed in the form of a thin film, normally in the range0.2 μm to 2 μm, obtained by coating onto the substrate undergoingprocessing, and then drying. A fine pattern can be obtained bypattern-exposure of this thin film using radiation such as an electronbeam, X-rays, vacuum ultraviolet or the like and then, following theexposure, carrying out baking and developing. In particular, the effectsare still more marked in the case where an electron beam is used.

The developing of the positive-working radiation-sensitive compositionof the present invention can be carried out using known developingliquids. As examples, there are aqueous solutions containing an alkalimetal hydroxide, carbonate, phosphate, silicate, borate or other suchinorganic alkali, 2-diethylaminoethanol, monoethanolamine,diethanolamine or other such amine, or tetramethylammonium hydroxide,choline or other such quaternary ammonium compound, or containing acombination of these.

EXAMPLES

Below, the present invention is explained in more specific terms byproviding examples but the invention is not to be restricted to theseexamples. Now, the weight average molecular weight in these examples isthe GPC (gel permeation chromatography) measurement value based onpolystyrene conversion. In the GPC measurements, there were used threeconnected GPC columns, “KF-804”, “KF-803” and “KF-802”, made by ShowaDenko K.K., and tetrahydrofuran was employed as the mobile phase, at aflow-rate of 0.8 ml per minute. The sample concentration was 0.2 wt %and the amount of injected sample was 0.1 ml. The detector was adifferential refractometer.

Example 1

A 60:40 (molar ratio) mixture of 1,1-diphenylethyl methacrylate andp-hydroxy-α-methylstyrene was polymerized at 70° C. in 1,4-dioxane usingazobisisobutyronitrile as the initiator, and a polymer of the followingchemical formula (11) obtained (weight average molecular weight 8200). 3g of this polymer and 300 mg of triphenylsulphonium triflate weredissolved in Methyl Cellosolve Acetate and, by filtering with a 0.2 μmfilter, there was obtained a resist composition.

The resist composition obtained was spin-coated onto a silicon waferwhich had been HMDS treated, after which heating was carried out for 2minutes at 100° C. and a resist film of film thickness 0.5 μm obtained.Using an electron beam exposure device, this resist film was subjectedto electron beam irradiation in the form of a pattern at an acceleratingvoltage of 20 kV. After heating for 2 minutes at 90° C., development wascarried out for 1 minute with 2.38% tetramethylammonium hydroxidesolution (ELM-D, produced by the Mitsubishi Gas Chemical Co.). At anexposure of 2.7 μC/cm², there was obtained a 0.20 μm pattern.

Example 2

A resist film was obtained in the same way as in Example 1 except thatthere was used polymer (weight average molecular weight 24000) of thefollowing chemical formula (12) instead of the copolymer employed inExample 1, and then election beam irradiation and development werecarried out. At an exposure of 3.9 μC/cm², there was obtained a 0.23 μmpattern.

Example 3

A resist film was obtained in the same way as in Example 1 except thatthere was used polymer (weight average molecular weight 10000) of thefollowing chemical formula (13) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 4.1 μC/cm², there was obtained a 0.23 μmpattern.

Example 4

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 9000) of thefollowing chemical formula (14) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.9 μC/cm², there was obtained a 0.22 μmpattern.

Example 5

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 7900) of thefollowing chemical formula (15) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.4 μC/cm², there was obtained a 0.19 μmpattern.

Example 6

Testing was carried out in the same way as in Example 4, except thatthere was used an 1-line stepper as the exposure device. At an exposureof 49 μJ/cm², there was obtained a 2.6 μm pattern.

Example 7

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 10000) of thefollowing chemical formula (16) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.6 μC/cm², there was obtained a 0.20 μmpattern.

Example 8

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 13000) of thefollowing chemical formula (17) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.7 μC/cm², there was obtained a 0.23 μmpattern.

Example 9

A resist film was obtained in the same way as in Example 1 except thatthere was used polymer (weight average molecular weight 13000) of thefollowing chemical formula (17) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.7 μC/cm², there was obtained a 0.23 μmpattern.

Example 10

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 26000) of thefollowing chemical formula (19) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.0 μC/cm², there was obtained a 0.21 μmpattern.

Example 11

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 58000) of thefollowing chemical formula (20) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.6 μC/cm², there was obtained a 0.22 μmpattern.

Example 12

Testing was carried out in the same way as in Example 10 except thatthere was used an 1-line stepper as the exposure device. At an exposureof 34 mJ/cm², there was obtained a 0.35 μm pattern.

Example 13

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 9700) of thefollowing chemical formula (21) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.6 μC/cm², there was obtained a 0.19 μmpattern.

Example 14

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 19000) of thefollowing chemical formula (22) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.9 μC/cm², there was obtained a 0.20 μmpattern.

Example 15

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 11000) of thefollowing chemical formula (23) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.4 μC/cm², there was obtained a 0.20 μmpattern.

Example 16

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 9500) of thefollowing chemical formula (24) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.2 μC/cm², there was obtained a 0.19 μmpattern.

Example 17

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 4500) of thefollowing chemical formula (25) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.0 μC/cm², there was obtained a 0.24 μmpattern.

Example 18

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 56000) of thefollowing chemical formula (26) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.5 μC/cm², there was obtained a 0.23 μmpattern.

Example 19

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 18000) of thefollowing chemical formula (27) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.4 μC/cm², there was obtained a 0.21 μmpattern.

Example 20

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 25000) of thefollowing chemical formula (28) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.7 μC/cm², there was obtained a. 0.20 μmpattern.

Example 21

Testing was carried out in the same way as in Example 13 except thatthere was used an i-line stepper as the exposure device. At an exposureof 29 mJ/cm², there was obtained a 0.31 μm pattern.

Example 22

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 23000) of thefollowing chemical formula (29) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.0 μC/cm², there was obtained a 0.19 μmpattern.

Example 23

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 18000) of thefollowing chemical formula (30) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.7 μC/cm², there was obtained a 0.22 μmpattern.

Example 24

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 57000) of thefollowing chemical formula (31) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.7 μC/cm², there was obtained a 0.22 μmpattern.

Example 25

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 35000) of thefollowing chemical formula (32) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.5 μC/cm², there was obtained a 0.21 μmpattern.

Example 26

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 4500) of thefollowing chemical formula (33) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.2 μC/cm² there was obtained a 0.23 μmpattern.

Example 27

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 18000) of thefollowing chemical formula (34) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.6 μC/cm², there was obtained a 0.20 μmpattern.

Example 28

Testing was carried out in the same way as in Example 22 except thatthere was used an 1-line stepper as the exposure device. At an exposureof 36 mJ/cm², there was obtained a 0.33 μm pattern.

Example 29

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 21000) of thefollowing chemical formula (35) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.7 μC/cm², there was obtained a 0.19 μmpattern.

Example 30

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 31000) of thefollowing chemical formula (36) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 2.4 μC/cm², there was obtained a 0.22 μmpattern.

Example 31

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 19000) of thefollowing chemical formula (37) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 1.6 μC/cm², there was obtained a 0.20 μmpattern.

Example 32

A resist film was obtained in the same way as in Example 1 except thatthere was used polymer (weight average molecular weight 8000) of thefollowing chemical formula (38) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.5 μC/cm², there was obtained a 0.24 μmpattern.

Example 33

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 11000) of thefollowing chemical formula (39) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.3 μC/cm², there was obtained a 0.22 μmpattern.

Example 34

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 9000) of thefollowing chemical formula (40) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out. At an exposure of 3.2 μC/cm², there was obtained a 0.22 μmpattern.

Example 35

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 14000) of thefollowing chemical formula (41) instead of the copolymer employed inExample 1, and then electron beam irradiation and development werecarried out.

At an exposure of 3.9 μC/cm², there was obtained a 0.23 μm pattern.

Example 36

Testing was carried out in the same way as in Example 34 except thatthere was used and i-line stepper as the exposure device. At an exposureof 36 mJ/cm², there was obtained a 0.33 μm pattern.

Comparative Example 1

A resist film was obtained in the same way as in Example 1 except thatthere was used poly(tert-butyl α-chloroacrylate) (weight averagemolecular weight 21000) instead of the copolymer employed in Example 1,and then electron beam irradiation and development were carried out. Atan exposure of 6.2 μC/cm², there was obtained a 0.33 μm pattern, and interms of sensitivity and resolution the properties were inadequate.

Comparative Example 2

A resist film was obtained in the same way as in Example 1 except thatthere was used copolymer (weight average molecular weight 12000) of thefollowing chemical formula (42) instead of the copolymer employed inExample 1, and then evaluation carried out.

At an exposure of 5.8 μC/cm², there was obtained a 0.25 μm pattern, andin terms of sensitivity and resolution the properties were inadequate.

The results are shown in Tables 1 and 2.

Industrial Application Potential

As described above, in the positive-working radiation-sensitivecomposition of the present invention a compound containing a specifiedacid labile group and an acid generator which generates acid as a resultof irradiation with radiation are employed, so that it is possible toobtained a composition of high resolution and high sensitivity.

TABLE 1 Examples Example Polymer 1

2

3

4

5

6 Same as Example 4 7

8

9

10

11

12 Same as Example 10 13

14

15

16

17

18

19

20

21 Same as Example 13 22

23

24

25

26

27

28 Same as Example 22 29

30

31

32

33

34

35

36 Same as Example 34 Example Mw Sensitivity (μC/cm²) Resolution (μm) 1 8200 2.7 0.20 2 24000 3.9 0.23 3 10000 4.1 0.23 4  9000 2.9 0.22 5 7900 2.4 0.19 6 Same as Example 4  49 mJ/cm² (i-line) 2.6  7 10000 1.60.20 8 13000 2.7 0.23 9  4400 3.0 0.23 10 26000 2.0 0.21 11 58000 3.60.22 12 Same as Example 10 34 mJ/cm² (i-line) 0.35 13  9700 1.6 0.19 1419000 1.9 0.20 15 11000 1.4 0.20 16  9500 1.2 0.19 17  4500 3.0 0.24 1856000 3.5 0.23 19 18000 2.4 0.21 20 25000 1.7 0.20 21 Same as in Example13 29 mJ/cm² (i-line) 0.31 22 23000 2.0 0.19 23 18000 2.7 0.22 24 570003.7 0.22 25 35000 2.5 0.21 26  4500 3.2 0.23 27 18000 1.6 0.20 28 Sameas Example 22 36 mJ/cm² (i-line) 0.33 29 21000 1.7 0.19 30 31000 2.40.22 31 19000 1.6 0.20 32  8000 3.5 0.24 33 11000 3.3 0.22 34  9000 3.20.22 35 14000 3.9 0.23 36 Same as Example 34 36 mJ/cm² 0.33

TABLE 2 Comparative Examples Comp. Ex. Polymer Mw Sensitivity (μC/cm²)Resolution (μm) 1

21000 6.2 0.33 2

12000 5.8 0.25

1. A positive-working radiation-sensitive composition comprising a) acompound with an alkali-soluble group protected by an acid labile groupa and b) an acid generator which generates acid by irradiation withradiation, wherein the acid labile group a has an alkali-soluble groupor alternatively the acid labile group a has an alkali-soluble groupprotected by an acid labile group b.
 2. A positive-workingradiation-sensitive composition according to claim 1 wherein the acidlabile group a with an alkali-soluble group protected by an acid labilegroup a has at least one phenolic hydroxyl group, or alternatively aphenolic hydroxyl group further protected with acid labile group b.
 3. Apositive-working radiation-sensitive composition according to claim 1wherein the acid labile group a in the compound with an alkali-solublegroup protected by an acid labile group a has at least one carboxylgroup or alternatively a carboxyl group further protected with acidlabile group b.
 4. A positive-working radiation-sensitive compositionaccording to claim 1 wherein the labile group a in the compound with analkali-soluble group protected by an acid labile group a is representedby general formula (4):

(R¹³ to R¹⁵ are each independently an alkyl group, a substituted alkylgroup, a cycloalkyl group, an aryl group, a substituted aryl group, agroup containing an alkali-soluble group, or a group containing analkali-soluble group protected by acid labile group b, and at least oneis a group containing an alkali-soluble group, or a group containing analkali-soluble group protected by acid labile group b, R¹³ to R¹⁵ may bethe same or different).
 5. A positive-working radiation-sensitivecomposition according to claim 4 wherein at least one of R¹³ to R¹⁵ ingeneral formula (4) is a group represented by general formula (5) or(6):

(A represents an alkylene group with 1 to 4 carbons, an arylene groupwith 6 to 10 carbons or a single bond, B represents an alkylene groupwith 1 to 6 carbons, an arylene group with 6 to 10 carbons, analkylenearylene group with 7 to 12 carbons or a single bond, R¹⁶ to R¹⁹each independently represents a hydrogen atom or an alkyl group with 1to 4 carbons, Y represents an acid labile group b or a hydrogen atom,and m is 1 to 3).
 6. A positive-working radiation-sensitive compositionaccording to claim 4 wherein at least one of R¹³ to R¹⁵ in generalformula (4) is a group represented by general formula (7):

(R²⁰ and R²¹ each independently represents a hydrogen atom or an alkylgroup with 1 to 4 carbons, Y represents an acid labile group b or ahydrogen atom, and m is 1 to 3).
 7. A positive-workingradiation-sensitive composition according to claim 4 wherein at leastone of R¹³ to R¹⁵ of general formula (4) is of structure represented bygeneral formula (8):

(R²² and R²³ represent a hydrogen atom or an alkyl group with 1 to 4carbons, Y represents an acid labile group b or a hydrogen atom).
 8. Apositive-working radiation-sensitive composition according to claim 1wherein the compound with an alkali-soluble group protected by an acidlabile group a is a polymer of weight average molecular weight from5,000 to 50,000.
 9. A positive-working radiation-sensitive compositionaccording to claim 1 wherein the compound with an alkali-soluble groupprotected by an acid labile group a is a polymer containing structuralunits represented by general formula (9):

(R²⁴ represents a hydrogen atom, an alkyl group with 1 to 4 carbons, acyano group or a halogen, Z is a group represented by general formula(1), (2) or (4)).
 10. A positive-working radiation-sensitive compositionaccording to claim 1 wherein the compound with an alkali-soluble groupprotected by an acid labile group a is a polymer containing structuralunits represented by general formula (10):

(R²³ represents a hydrogen atom, an alkyl group with 1 to 4 carbons, acyano group or a halogen, X is an acid labile group represented bygeneral formula (2) or (4)).
 11. A positive-working radiation-sensitivecomposition according to claim 9 wherein R²⁴ is a cyano group or ahalogen.
 12. A positive-working radiation-sensitive compositioncomprising a positive-working radiation-sensitive composition containinga) a compound with an alkali-soluble group protected by an acid labilegroup a and b) an acid generator which generates acid by irradiationwith radiation, and any of the following conditions a1) to a3) aresatisfied: a1) The alkali-soluble group is a carboxyl group and the acidlabile group is represented by general formula (I)

(R¹ and R² are aromatic rings, and R³ represents an alkyl group, asubstituted alkyl group, a cycloalkyl group or an aromatic ring; and R¹to R³ may be the same or different) a2) The acid labile group isrepresented by general formula (2)

(R⁴ to R⁶ are each an alkyl group, a substituted alkyl group, acycloalkyl group or an aromatic ring, and at least one of R⁴ to R⁶ is anaromatic ring with an electron-donating group; and R⁴ to R⁶ may be thesame or different) a3) The acid labile group a has an alkali-solublegroup or alternatively the acid labile group a has an alkali-solublegroup protected by an acid labile group b,  and wherein the compoundmeeting any of conditions a1) to a3) is a polymer containing structuralunits represented by general formula (9):

(R²⁴ represents a hydrogen atom, an alkyl group with 1 to 4 carbons, acyano group or a halogen, Z is a group represented by general formula(1), (2) or (4)).
 13. A positive-working radiation-sensitive compositionaccording to claim 12 wherein condition a2) or a3) is satisfied andwherein the compound meeting condition a2) or a3) is a polymercontaining structural units represented by general formula (10):

(R²³ represents a hydrogen atom, an alkyl group with 1 to 4 carbons, acyano group or a halogen, X is an acid labile group represented bygeneral formula (2) or (4).
 14. A positive-working radiation-sensitivecomposition according to claim 12 wherein R²⁴ is a cyano group or ahalogen.